Abstract:

Results of two wavelength lidar sensing of middle atmosphere are presented at altitude range of 30 to 60 km over Obninck (55.1° N., 36.6° E) in 2012–2017. Monthly mean values of the ratio of coefficients of aerosol and Rayleigh backscattering (RCAR) at 532 nm wavelength averaged through 40–50 km and 50–60 km altitude layers are varied from 0 to 0.02, meanwhile mean peak levels of RCAR at the same layers are changed from 0.1 to 0.2. Short-time (about month) and long-time (half-year and longer) variations in backscattering are observed. Short-time variations are coordinated with meteor shower bursts. Long-period enhancements of backscattering were observed in 2013 after Chelyabinsk meteorite fall and also in the first half of 2016. In 2014–2015, the monthly mean RCAR was zero within measurement error at altitudes of 40–60 km.
A possibility of long-time manifestation of meteoric aerosol in backscattering is analyzed taking into account incoming meteoric mass, gravitational sedimentation of meteoric particles, and vertical wind. It is shown that incoming masses of visible meteor with mass greater than 10-6 kg and bolides are not sufficient for long-time enhancements of backscattering at 50–60 km layer. It is proposed that the most probable cause of backscattering enhancements is the formation of size enlarged fraction of meteoric smoke particles produced at meteor ablation and transported to upper stratosphere within polar stratospheric vortex. In the beginning of 2016, the formation of extremely intensive polar vortex and it’s displacement to Eurasia contributes to this phenomena.